Nanotech Filter Separates Oil and Water

A scanning electron microscopy image of the carbon nanotube-coated filter. For comparison,
the inset is bare stainless steel mesh.

Water and oil may not mix, but, like two boxers nearing the end of the final round,
they can get awfully tangled up.

Now, Michigan Technological University scientists Yoke Khin Yap and Jaroslaw Drelich
have created a filter that separates the two substances as quickly and cleanly as
a ref breaking up a clinch.

Their fine, stainless steel mesh is coated with carbon nanotubes about 10 microns
across. “They have a super-honeycomb structure that repels water,” says Yap, an associate
professor of physics. “But they like organic stuff, like oil.”

The team poured an emulsion of water and gasoline over the filter to test it. Sure
enough, the gas dripped through; all but 20 percent of the water stayed put.

It’s not as if you could filter the Gulf of Mexico through the device, Yap cautions.
Their prototype is about the size of a quarter. Plus, the water drops can actually
clog the spaces between the nanotubes, making it hard for anything to get through.
“But the attractive thing is that it’s so simple,” he says. “It runs by gravitation.”

Drelich, an associate professor of materials science and engineering, thinks the filter
has real-world potential. “These were just our first set of experiments,” he says.
“We could supply electricity to it to heat it up, reducing the oil’s viscosity and
evaporating the water. We could also create a vacuum that would suck oil through the
filter to the other side. A good engineering design could get rid of clogging problem.”

Such technology could help purify oil from Canada’s tar sands, which is contaminated
by traces of corrosive salt water. Or, it could be used to recover oil from the wastewater
of ocean-going vessels. It might even be able to scrub the oil inside your car’s engine.

“Our design would be completely novel, because it relies on nanotechnology, and it
could be competitive,” says Drelich.

Their work was published in the Feb. 2 edition of the journal Carbon and is funded
by the National Science Foundation.

Michigan Technological University is a public research university, home to more than
7,000 students from 60 countries around the world. Founded in 1885, the University
offers more than 120 undergraduate and graduate degree programs in science and technology,
engineering, forestry, business and economics, health professions, humanities, mathematics,
and social sciences. Our beautiful campus in Michigan’s Upper Peninsula overlooks
the Keweenaw Waterway and is just a few miles from Lake Superior.